Reformatted computed tomography to assess the internal nasal valve and association with physical examination.

Abstract

Objectives: To assess the cross-sectional area and angle of the internal nasal valve more accurately by reformatting computed tomography (CT) scans of the nasal airway according to a more appropriate orientation than scans traditionally sectioned in the coronal plane and then to compare the results with clinical data on the nasal valve obtained from physical examination.

Methods: We performed a retrospective review of the medical records of 24 rhinoplasty patients treated at a private practice facial plastic surgery office affiliated with a tertiary care university hospital. The patients had fine-cut (0.75-mm section) CT scans ordered for nasal airway obstruction or nasal valve compromise at the same institution. These patients were evaluated from January 1, 2000, through December 31, 2010. The previously acquired CT scans were reformatted to obtain sections through the internal nasal valve at a more appropriate orientation. The internal nasal valve cross-sectional area and valve angle were measured through a standardized section (1 cut immediately anterior to the head of the inferior turbinate) from the reformatted scans. The cross-sectional area was also measured through the same point on the traditionally oriented CT scan, and the values were compared. The results from each patient's scan were compared with data from the patient's medical record and analyzed against the patient's preoperative modified Cottle examination findings.

Results: The CT scans oriented in the reformatted plane through the internal nasal valve provided a narrower valve angle than the traditionally oriented CT scans and more closely approximated the hypothesized true value of the internal nasal valve of 10° to 15° (P < .001). In a comparison of the same-side internal nasal valve angle and cross-sectional nasal valve area between the 2 different CT scan orientations, a statistically significant difference in the internal nasal valve angles between the 2 scan orientations was discovered, but this finding did not reach significance when distinguishing the nasal valve cross-sectional area. Finally, no correlation was found with regard to the preoperative modified Cottle maneuver scores for the internal nasal valve angle and cross-sectional valve area values in either scan orientation.

Conclusions: Precise preoperative evaluation of the internal nasal valve is critical to the workup for reconstruction or repair of problems that involve this area. Although tools such as acoustic rhinometry exist to evaluate the cross-sectional area of the nasal valve, many rhinoplasty surgeons do not have access to this expensive equipment. A CT scan with reformatting in the proper plane of the internal nasal valve can provide the surgeon with improved anatomical information to assess that region. With this in mind, however, the surgeon should always perform a thorough preoperative physical examination and treat the patient and his or her symptoms, not the imaging studies, when considering a candidate for a surgical intervention.